问题描述
可以在Boost图表库中使用捆绑的属性,使用标准库类型,同时还使用< 流运算符的类型重载满足
write_graphviz
?
Is it possible to use bundled properties in the Boost Graph Library, with a standard library type, while also using that type's overload of the <<
stream operator to satisfy write_graphviz
?
#include <boost/graph/graphviz.hpp>
namespace boost {
namespace detail {
namespace has_left_shift_impl {
template <typename T>
inline std::ostream &operator<<(std::ostream &o, const std::array<T,2> &a) {
o << a[0] << ',' << a[1];
return o;
}
}
}
}
static_assert(boost::has_left_shift<
std::basic_ostream<char>,
std::array<double,2>
>::value,"");
int main()
{
using namespace boost;
typedef adjacency_list<vecS, vecS, directedS, no_property, std::array<double,2>> Graph;
Graph g;
add_edge(0, 1, {123,456}, g);
write_graphviz(std::cout, g, default_writer(),
make_label_writer(boost::get(edge_bundle,g)));
return 0;
}
面对Boost静态断言,我修改了我的代码;采纳的建议,其中 <
实现在 boost :: detail :: has_left_shift_impl
命名空间中定义。唉,我现在面临另一个错误:
Faced with a Boost static assert, I modified my code to that above; adopting a suggestion from here, wherein the <<
implementation is defined within the boost::detail::has_left_shift_impl
namespace. Alas, I'm now faced with another error:
/usr/include/boost/lexical_cast.hpp:1624:50: error: cannot bind ‘std::basic_ostream<char>’ lvalue to ‘std::basic_ostream<char>&&’
bool const result = !(out_stream << input).fail();
code>可以由 write_graphviz
使用?我使用的是Ubuntu 14.10和GCC 4.9.1。
Is there a way to provide an overload of <<
which can be used by write_graphviz
? I'm using Ubuntu 14.10 and GCC 4.9.1.
推荐答案
你甚至不能做
std::cout << g[add_edge(0,1,{123,456},g)];
不提供
inline static std::ostream& operator<<(std::ostream& os, std::array<double, 2> const& doubles) {
return os << "{" << doubles[0] << "," << doubles[1] << "}";
}
现在得到 lexical_cast
在正确的时间是非常难以移植(主要是因为ADL不会帮助你 std :: array
和 double
)。
Now getting these overloads seen by lexical_cast
at the right time is exceptionally hard to do portably (mostly because ADL won't help you with std::array
and double
).
可以使用值转换属性映射(当然是readonly):
Instead you can use a value transforming property map (which is readonly of course):
std::string prettyprint(std::array<double, 2> const& arr) {
std::ostringstream oss;
oss << "{" << arr[0] << "," << arr[1] << "}";
return oss.str();
}
然后 make_transform_value_property_map(prettyprint,get(edge_bundle, g))
#include <boost/graph/adjacency_list.hpp>
#include <boost/graph/graphviz.hpp>
using namespace boost;
std::string prettyprint(std::array<double, 2> const& arr) {
std::ostringstream oss;
oss << "{" << arr[0] << "," << arr[1] << "}";
return oss.str();
}
int main()
{
using namespace boost;
typedef adjacency_list<vecS, vecS, directedS, no_property, std::array<double,2>> Graph;
Graph g;
add_edge(0, 1, {123,456}, g);
write_graphviz(std::cout, g, default_writer(),
make_label_writer(make_transform_value_property_map(&prettyprint, get(edge_bundle, g))));
}
列印
digraph G {
0;
1;
0->1 [label="{123,456}"];
}
这篇关于为GraphViz的Boost图捆绑输出重载流运算符的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持!